UsdAttributeSet

In USD, the attributes are essentially the defining properties of the prim. As a simple example, one of the properties of cube prim is “size”, which could appear as follows:

#usda 1.0
def Cube "myCube"
{
float size = 2.0
}

An attribute has a data type (the type is “double” in the example above), name, and value. The value may be numeric, a string, or an array. Unlike metadata, the value of an attribute may be time-sampled, in that the attribute may have several values, each of which is active at a given timecode or frame.

Attributes are one of the two defining properties of a prim, together with relationships.

Note:  For more details see Attribute in OpenUSD’s USD Glossary.

Setting and Blocking Attributes

When assigning an attribute to a prim, you can choose between one of three actions:

  • Create/Override - Add a new attribute or override the value of an existing one.

  • Block - Disable the attribute, effectively blocking its effect on the prim.

  • Force Default - Force the attribute back to its default value.

As Block and Force Default don’t require a value, you need only supply the attributeName.

Create/Override requires all the attribute settings including attributeName, attributeType, and value. You also need to set isCustom to indicate if the attribute is pre-defined or a new, custom attribute.

For time-sampled values, set multisample to Yes. For example, say you’re animating a cube to grow in size, the attribute in USD code, could look like this:

def Cube “GrowingCube"
{
float size.timeSamples = {
  0: 1.0,
  2: 2.0,
  3: 4.0,
}
}

Tip:  You can drag and drop an attribute from the Attributes Tab into the UsdAttributeSet node's Parameters to have it adopt the attributeName, attributeType, and value.

Inputs

Connection Type

Connection Name

Function
input in The incoming scene graph data that the node will operate on or modify.

Controls

Control (UI)

Default Value

Function
primPaths N/A The paths to the Prims that you want to assign this attribute to.
action  

Choose how you want to apply the attribute update.

  • Create/Override - Create the attribute, or if it exists already, assign the new value.

  • Block - Disable the attribute assignment in the prims, removing their effect from stage composition.

  • Force Default - Force the attribute to adopt its default value.
attributeName N/A Assign a name to the attribute.
attributeType Double Choose from one of the available data types for the attribute.
multisample Yes

Select Yes if the data is time-sampled.

Select No if the value should not vary over time.
isCustom No Select Yes if this is a custom attribute.
value N/A Assign a value to the attribute.